Electrical braking device for vehicle trailers and method for operation thereof

1. An electric brake device for vehicle trailers with a trailer travel direction and with a rigid hitch arrangement with a rigid member section extending in a rigid member section axial direction to a trailer coupling, the rigid member section axial direction being generally in the trailer travel direction, the device comprising:

a brake means having a power supply unit that can be connected to a towing vehicle;

a sensing means designed as a deformation-sensing device, mounted at the rigid hitch arrangement on the rigid member section for detecting deformation in the rigid member section and for determining the axial direction tensile and compressive forces acting in the rigid member section of the hitch arrangement in the rigid member section axial direction along the rigid section without movement of the hitch arrangement relative to the trailer coupling; and

a control for determining the braking force needed based on the detected axial direction tensile and compressive forces and braking the trailer with the braking forces needed with the braking means.

2. A brake device in accordance with claim 1 , wherein the deformation-sensing device has a plurality of electric wire strain gauges.

3. A brake device in accordance with claim 2 , wherein the wire strain gauges are arranged on both sides at the rigid member section having massive walls.

4. A brake device in accordance with claim 2 , wherein the wire strain gauges are arranged in an area of a neutral axis of the member section.

5. A brake device in accordance with claim 1 , wherein the rigid member section is a straight member section rigidly connected with the trailer coupling.

6. A brake device in accordance with claim 5 , wherein the member section is made in one piece with a coupling housing of the trailer coupling.

7. A brake device in accordance with claim 1 , wherein the member section is rigidly connected with the hitch arrangement by means of a fastening means with a clamp and screw connection.

8. A brake device in accordance with claim 1 , wherein the member section is fastened to a mounting fitting with a hitch plate, with a clamping part surrounding the member section on the outside.

9. A brake device in accordance with claim 8 , wherein the deformation sensing device comprises a plurality of strain gauges and the wire strain gauges are arranged at the member section axially in the middle area between the trailer coupling and the clamping part.

10. A brake device in accordance with claim 1 , wherein a mounting fitting has an axial hump for guiding the member section.

11. A brake device in accordance with claim 1 , wherein a mounting fitting is rigidly connected with the front end of one or more hitch ties.

12. A brake device in accordance with claim 1 , wherein the control is arranged in the member section.

13. A brake device in accordance with claim 12 , wherein the vehicle trailers comprise a chassis with crossties and the brake means comprises electric wheel brakes and electric control lines are installed to the electric wheel brakes in the crossties of the chassis.

14. A brake device in accordance with claim 1 , further comprising the power supply unit of the electric brake means has a connection cable with contacts for connection with lines for brake light and permanent plus of the towing vehicle.

15. An electric brake device, in accordance with claim 11 , wherein a brake head designed as an add-on piece for the hitch arrangement includes the trailer coupling with the member section, the wire strain gauges, the control, the power supply unit and the mounting fitting.

16. A process for actuating an electric brake device of a vehicle trailer, which is equipped with a rigid hitch arrangement and a trailer coupling, wherein the brake device has a power supply unit, which can be connected to a towing vehicle, said electric wheel brakes and a sensing means as well as a control for determining and introducing the necessary braking forces, the process comprising the steps of:

providing the rigid hitch arrangement with a rigid member extending to the trailer coupling in a travel force transmission direction that is along the rigid member between said rigid connection with the trailer coupling and the wheels;

providing wire strain gauges mounted at the rigid member; and

sensing deformation at the vehicle trailer during the braking of the towing vehicle at the rigid member of the rigid hitch arrangement to determine axial tensile and compressive forces acting in the rigid member of the hitch arrangement in the travel force transmission direction, without movement of the hitch arrangement relative to the trailer coupling based on the force transmission direction compressions or strains in the rigid member by means of said wire strain gauges;

using a control to determine the braking force needed based on the detected axial tensile and compressive forces; and

braking the trailer with the braking device based on the determined braking forces needed.

17. A vehicle trailer brake system, comprising:

a trailer with a trailer coupling, a rigid member section extending between a rigid connection with the trailer coupling and wheels connected to the rigid member section and having a rigid member axial direction along a path of said rigid member between said rigid connection with the trailer coupling and the wheels;

electric wheel brakes acting on the wheels for braking the trailer, the brakes having a power supply unit with means for connection to a power source of a towing vehicle;

a deformation-sensing device mounted at the rigid member section to determine the rigid member axial direction tensile and compressive forces acting in the rigid member section in the rigid member axial direction, without movement of the rigid member section relative to the trailer coupling; and

a control for determining a braking force needed based on the detected axial tensile and compressive forces sensed and braking the trailer with the braking forces needed with the electric wheel brakes.

18. A brake device in accordance with claim 17 , wherein the deformation-sensing device comprises a plurality of electric wire strain gauges on the rigid member section.

19. A brake device in accordance with claim 18 , wherein the wire strain gauges are arranged on both sides at the rigid member section having massive walls and the wire strain gauges are arranged in the area of a neutral axis of the rigid member section.

20. A brake device in accordance with claim 19 , wherein the rigid member section is a straight member section rigidly connected with the trailer coupling.